Wheels or rims for truck tires and like heavy duty pneumatic tubeless tires can be of the so-called steep-shoulder type wherein the outer surface of the felly against which the inner edges of the beads of the tire rest are frustoconical with an apex angle of about 30.degree. . This means that at any point along the felly, this surface includes an angle of about 15.degree. with the axis or with a line parallel to the axis, i.e. a horizontal. The outer flange of the rim may include a slight angle with the vertical and rises at an obtuse angle from the aforementioned surface of the felly to flank the bead.
It is known to provide pneumatic tires for such wheels (see French Pat. No. 1,281,439) in which the tire bead has a core which is formed in part by a plurality of layers of steel strip or band, the ends of the layers being fixed by spot welding or adhesive binding which also prevents relative shifting of the layers.
The bead core formed in this manner serves to improve the anchoring of the carcass reinforcement, e.g. the steel bands or cords which pass beneath and around the bead core, thereby stabilizing the tire.
In spite of the attempts made to prevent relative shifting of the layers in this earlier system, some shifting can occur and various expedients have been proposed to limit the possibility of shifting. These techniques include winding a further band around the stack or otherwise tying the bands together.
This has been found to be impractical, time-consuming and expensive from a manufacturing point of view and also has the disadvantage that any devices used to hold the layers in place tends to excessively space the steel belts or, more generally, the carcass reinforcement from the bead core and reduce the stability of the tire.
Furthermore, since the tie means are generally wound helically around the layers of the bead core, some of the steel cords can be closer to the core than others and as a result the carcass reinforcement is not of uniform tension throughout, thereby leading to distortion, early tire wear, and to weak points at which rupture may occur.
When the tire is fully built using the teachings of the prior art, it frequently is out of round in places and the large scale production of tires seldom is able to produce two substantially identical tires because of these problems. Thus fabrication of the tires is not consistent.
Finally, experience has shown that in the conventional approach the steel belts (carcass reinforcement) frequently encounters sharp edges of the bead core so that with time the belts are damaged, tire wear is increased and the danger of blowout is heightened.